[Pete]

Many people that build engines as a HOBBY, forget that "TIME IS MONEY".
1- There is almost always unlimited time available.
2- There is almost always VERY limited money available.

If you have a lathe or have access to one, MAKE YOUR OWN STUDS.
20 bucks will get you enough 7/16 4340.
Another 20 bucks will get them heat treated to 40RC.
Big advantage of doing it his way is, you can tailor the fit to the threads in YOUR block.
You know they will be sitting straight when installed.
You coat the threads with high temp RTV, screw them in to bottom and back up 1/2 turn, with fingers only, let them sit over night and they never leak.

Use HARD high nuts and HARD machine washers all lubed with EP gear oil for accurate torque or stretch readings.

Do not use stainless washers. They are not hard enough and will almost certainly gall at some point.

Remember, unless you are building on a deadline, this is the cheapest and BEST QUALITY way to go.
On those long winter nights, fill your shop ice box with your favorite beverage, light a fire in the stove, Move the hound dog's bed over by the stove and give him a big leg bone to knaw and fire up the lathe.